In air-conditioning in e.g., a railcar, an air conditioner sucks interior air of a passenger car through suction openings, and discharges temperature-regulated air as a conditioned air into an interior of the passenger car through outlets provided on the right and left sides of a carbody or on the right and left sides of a ceiling of the interior. At this time, each of the conditioned air discharged from the outlets on the right and left sides of the carbody into the interior is merged at a central part in a passenger car width direction and becomes descending air flow at the central part to be blown.
When the descending air flow is generated at the central part, any problem is not caused in a passenger car with an aisle located at the central part of the passenger car. However, in a passenger car in which the number of seats differs between the right and left sides, for example three-row seating and two-row seating, the descending air flow is blown on the passenger sitting on the aisle seat in the three-row seating side. An air flow giving uncomfortable feeling to a passenger is called as a “draft”. In order to prevent the “draft” from occurring in the interior, it is necessary to reduce the air speed of the conditioned air to a certain extent or less in the interior.
As a conventional technique for preventing the occurrence of the “draft”, technique of Patent Document 1 has been disclosed, the technique assuming the passenger car whose seating capacity differs between the right and left sides like e.g., three-row seating and two-row seating. The invention in the Patent Document 1 suggests the technique that a ratio of air volume discharged from the right and left sides is optionally regulated to generate the descending air flow above the aisle located different from the central part. The invention of the Patent Document 1 assumes that it will be best when the ratio of air volume between the three-row seating and the two-row seating is set in 54:46.